Thursday, November 03, 2011

High Dynamic Range (HDR)

In my previous blog about the off camera flash (read more here) I mentioned I would take the photo of the original scene and use other photoshop techniques to improve it. Here is the original image for you to have a look at.

As you can see it is a bit dark and also very flat. To improve the image I decided to use some HDR (high dynamic range) technique. High dynamic range is a technique whereby we use images with different exposure values of the same scene and overlay /combine them into one photograph.
If you want to use the technique you require multiple images of the same scene with different exposures. You can either use your tripod  and take multiple images using your bracketing function on your camera or use manual exposures. I recommend at least one f-stop apart and a minimum of 5 images. This will give you darker images when the image is underexposing as well as some high key images that are overexpose.
The idea is that we exposure all part of the image correctly and get the colour range for all areas including the shadows in the correct exposure.
The technique that I was using is slightly different. As I am shooting raw I can change the image exposure in  Photoshop or Lightroom. So I created 4 virtual copies of the same image in Lightroom and changed the exposure compensation to -1, 0 , 1, 2, 3. I then exported the images into Photomatix a HDR software tool that integrates with Lightroom.
You can also use Photoshop's HDR function, but I prefer Photomatix which has a lot better controls. Here is the result of the HDR transition.
The advantage of using the Lightroom technique is that the image is the same for all images. The technique with the tripod and the bracketing has the disadvantage that anything that is moving in the image such as clouds will blur in the combined HDR image.
As you can see with the image above we go t already a nice image that has a fair bit of detail quite nice colours and the shadows are reduced. I did not like the image in this format too much because as with many images in the forest the detail in the brush creates too much clutter in the image.
So with a vignette and maybe a bit of grain I might be able to give the image a bit more structure and and reduce the clutter. I started off with a black vignette, but for this image I did not feel I wanted to do this again. Instead I decided on a white vignette with low opacity and quite a large size.

This is bringing tree and the bridge more in the foreground and it looks now as if there is a bit of fog. I use Colour Efex filters for this sort of technique. You can also create a Curves layer above your image and use the lasso selection tool to create a selection around the image. Make it uneven to make it look more natural. You then refine the edges of the selection to a high feather value such as 45 or 50. Last but not least you create a mask on the curves layer which than creates your vignette if you made the selection before hand.
I hope this little article helps you and inspires you to get into HDR photography. At my Facebook album for HDR you can see other HDR examples.  
Achim Drescher is the principal photographer at AD Photography. Click here to find out more.